A regular full-time employee may be granted a leave of absence without pay upon written application approved by his/her department head and the city administrative officer. Such leave may not exceed six months’ time. Such leave shall be granted only in those cases where an employee’s record of service makes it desirable for the city to retain his/her services even at the cost of some inconvenience to the city or when an employee’s application for disability retirement is pending and no other leave is available. An employee on such an approved leave shall not accrue seniority or other benefits during the leave period. Failure of an employee to report promptly at the expiration of the leave, or within a reasonable time after notice to return to duty, shall be cause for dismissal. The mailing by U.S. mail of a first class letter postage paid, addressed to the employee’s last known address, shall be reasonable notice. (Prior code § 2708.9)